Test of steel prototype for border wall showed it could be sawed through

President Donald Trump has repeatedly advocated for a steel slat design for his border wall, which he described as "absolutely critical to border security" in his Oval Office address to the nation Tuesday. But Department of Homeland Security testing of a steel slat prototype proved it could be cut through with a saw, according to a report by DHS.

A photo exclusively obtained by NBC News shows the results of the test after military and Border Patrol experts were instructed to attempt to destroy the barriers with common tools.

The Trump administration directed the construction of eight steel and concrete prototype walls that were built in Otay Mesa, California, just across the border from Tijuana, Mexico. Trump inspected the prototypes in March 2018. He has now settled on a steel slat, or steel bollard, design for the proposed border barrier additions. Steel bollard fencing has been used under previous administrations.

However, testing by DHS in late 2017 showed all eight prototypes, including the steel slats, were vulnerable to breaching, according to an internal February 2018 U.S. Customs and Border Protection report.